The long-term objective of this project is a better understanding of infant and toddler motor development. Specific aims include the development and validation of new strategies for analyzing motor behavior with emphasis on quality of movement. Quality of movement will be operationalized as: 1) variations within a position, 2) transitions within a position, 3) complex combinations of single motor events, and 4) the number of abnormal movement patterns. The sample will be 390 normal and 90 high-risk children. Analyses will focus on determining normative motor patterns, developmental age trends, high-risk/normal group differences, and reliability. Unlike traditional approaches to motor assessment, the proposed observation system evaluates movement in the context of spontaneous, naturally- occurring play. Motor assessments that involve direct handling of the child have consistently been found to be unreliable. The new approach minimizes the uncontrolled-for effects of examiner-examinee interactions because little handling is required. The responsible implementation of Public Law 99-457 demands reliable and valid observational techniques for use with infants and toddlers. The proposed research is theoretically and clinically meaningful and likely to be of value in evaluating motor development and predicting risk.